The dura mater is located between the cranium and the brain and around the spinal cord. It principally protects the brain and spinal cord and prevents cerebrospinal fluid leakage. Defects or contractures of the dura mater need to be compensated for and lyophilized human dura mater has been used for that purpose. However, human dura mater has drawbacks such as low homogeneity and limited supply. Further, possible transmission of Creutzfeldt-Jakob disease through the use of human dura mater was reported (Noshinkeigeka; 21(2), 167–170, 1993) and, eventually, the Japanese Ministry of Health and Welfare banned the use of lyophilized human dura mater on Apr. 7, 1997.
To solve the above problems, an artificial dura mater made of silicone was developed. However, silicone dura mater has fallen into disuse as it was reported that silicone dura mater creates a predisposition to meningorrhagia by remaining permanently in vivo because it is non-biodegradable, chronically stimulating the surrounding tissue and causing hypertrophy of the granulation tissue.
In contrast, artificial dura maters made of biodegradable and bioabsorbable materials such as collagen (Journal of Biomedical Materials Research; Vol. 25 267–276, 1991) and gelatin (No to Shinkei; 21 1089–1098, 1969) were produced, but they are not in practical use because of strength-related problems, i.e., because their suture strength is insufficient to allow them to be sutured integrally with the dura mater.
The applicant provided, in Japanese Unexamined Patent Publication No. 1996-80344, not only an artificial dura mater comprising a sheet made of a biodegradable and bioabsorbable polymer, for example, a copolymer of lactic acid and caprolactone, but also an artificial dura mater further comprising a biodegradable and bioabsorbable polymer made of a material different from that of the sheet as reinforcement between sheets and an integral molding of the sheets and the reinforcement.
The applicant also provided an artificial dura mater which showed improved non-leakage and suture strength, etc. and a production method thereof, as well as an artificial dura mater which allows optical observation of the brain inside.
However, the criteria of flexibility, inhibition of the cerebrospinal fluid leakage, and mechanical strength, etc. required in the artificial dura mater when used medically were not discussed in detail.
An object of the present invention is to additionally propose the constituent components necessary for an artificial dura mater and their properties.